As the 20-year-old student sweeps to victory in Paisley and Renfrewshire
South, Jim Murphy, the Scottish Labour leader, is defeated in his seat

Mhairi Black, the UK’s youngest MP since the 17th century, claimed the SNP’s most remarkable scalp north of the border, and is poised to become one of Westminster’s most unlikely parliamentarians.

The 20-year-old law student, who is in fourth year at Glasgow University, secured the biggest upset of the 2015 general election so far by beating Douglas Alexander in Paisley and Renfrewshire South by more than 6,000 votes.

She was only two when her opponent swept to power under Tony Blair in 1997, and only joined the SNP last year.

But she has long been schooled in her disdain for “new Labour”, and her loathing of Margaret Thatcher, by her father Alan, a 55-year-old retired teacher who she says was once a “diehard” Labour man.

Ousted... Douglas Alexander

Miss Black emerged as a firebrand advocate of independence during last year’s referendum campaign after giving up her job in the Pizza Mario chip shop to concentrate on politics.

She may now be on message - after Nicola Sturgeon’s insistence that even if the SNP won every seat it would not be a mandate for a second referendum - but she did say in her candidate statement that a large block of SNP MPs could be used as the rope that a “hung parliament hangs on”.

That chimed with her comments in a speech last year when she said she would seek to twist Westminster’s arm to force another vote on breaking-up Britain.

She added: “When you are talking to all these Yes campaigners the morale is stronger now than it was before. My mum said to me, obviously when I was heartbroken about the result, she said to me, ‘See if you can ride this out, youse are unstoppable’.

“The No side can feel how inevitable independence is. It is coming and it is coming quick, because you have 1.6 million people who want out of this union.”

Not surprisingly, she is undergoing something of a transformation. As a member of Twitter since she was 14, she has had to delete a number of ill-advised and foul-mouth teenage tweets - but not before they were spotted by her opponents.

She called Smirnoff Ice the “drink of gods”, said she “f****** hated Celtic” - she is a keen Partick Thistle supporter - and talked about waking up beside beer cans and pizza.

She also admits that being caught on camera saying she wanted to “stick the nut on” - head butt- Labour councillors after the referendum result was not the “wisest phrase”,insisting it was typical west of Scotland tongue banter.

She has repeatedly dismissed Westminster politicians as “men in suits”, but was taken suit shopping by her mother after becoming a high-profile candidate.

However, Miss Black still insists she will “never totter up in a skirt and heels”, even if the leader of her party does on a daily basis.

In a recent interview she added: “I am taking my dress sense a bit more seriously. I’ve had to recognise that, if I am to represent a wide range of people, I have to smarten up. I’m trying to look the part.”

The youngest MP since 13-year-old Christopher Monck in 1667, she received 23,548 votes compared to Mr Alexander’s 17,854.

She says she joined the SNP after witnessing “the level of poverty and injustice prevalent in our society”, and recalls learning what the words social justice meant in a modern studies class at school.

She describes social justice as her main motivation and sees plenty of injustice, and a need for change, in her rundown hometown of Paisley.

On her website she adds: “I truly believe that the only way to bring the powers we were promised, and the social justice that Scotland so desperately needs, is to have a strong “roup of SNP MP's at Westminster to ensure our voices are heard.?

With the reference to independence removed, that is the new scrubbed up version of her political raison d’etre.

It is a far cry from her claim during the campaign that No voters were “gullible”, and her father’s claim in a YouTube video that they could be divided into four categories - the bigoted, the selfish, the frightened and the deluded.

Those who voted for her defeated Labour opponent will not be so easily convinced that the SNP’s youngest leopard has changed its spots.